Preparation of grafted polymer compositions



United States Patent PREPARATION OF GRAFTED POLYMER COL [POSITIONS Lon Adany, Champignysur-Marne, France, assignor to Societe Anonyme dite: Nobel-Bezel, Paris, France No Drawing. Filed Mar. 31, 1958, Ser. No. 724,932 Claims. Cl. 204-154 This invention relates to the preparation of polymerized compositions, more especially by grafting techniques. In so-called grafting oopolymerization processes, a polymerizable monomer is molecularly combined with a. carrier substance by the use of an activation process which may comprise any of various mechanical, physical 'and chemical operations. One particularly advantageous method of activating a monomer and carrier mixture to promote graft-copolymerization thereof, involves irradiating one or both constituents of the mixture with ionizing radiation. It is to this particular class of graft copolymerization processes that the present invention more particularly relates, and objects hereof are to provide improved techniques for the preparation of radiationgrafted copolymers, and also to provide grafted polymer compositions having improved characteristics.

The invention is especially concerned with the nature of the carrier used. Thus one aspect of the invention relates to a'method of graft-copolymerizing at least one polymerizable vinyl-base monomer with a carrier comprising at least one saturated parafiinic hydrocarbon (i.e. of the type C H J The carrier may form of a mixture of hydrocarbons 'containg a proportion of not more than 20% of unsaturated hydrocarbons as impurities therein.

The saturated hydrocarbons usable according to the invention may include broadly all solid hydrocarbons, iJexhaving a boiling point higher than about 300 C. and a melting range offrom 55 to 70 C., as derived from the distillation of tars, wood, turf, lignite, bituminous shale, and also Vaseline which has a melting point of from 30 to 40 C. Substituted paraifins such as chlorinate d parafiines may also be used. Practically the saturatd hydrocarbons used will frequently be derived from natural sources, and will usually comprise mixtures. While the exact composition of such mixtures need not be fully determined, it is useful or necessary for the purposes of the invention that the proportion of unsaturated hydrocarbons in the mixtures, such as hydrocarbons having the general formulas such as C H C H and the like, should not exceed about 20% The polymerizable vinyl-base monomer used as the graft substance according to the invention may include any vinyl monomer. However, it is preferred to use those vinyl monomers that are liquid at ordinary temperatures such as vinyl acetate, styrene, and acrylonitrile, and the invention is especially concerned with a preparatory or conditioning step applicable to such monomers prior to grafting them on saturated hydrocarbons of the type specified above.

The preparatory step is necessary because, as is known, such monomers are practically not miscible with paraffins at ordinary temperature. At higher temperatures however the monomers become soluble in the paraflins, usually even below the boiling point of the latter. It has been found that the resulting solutions when cooled at a slow enough rate produce stable and homogeneous gels.

It has further been found that when such gels are exposed to ionizing radiations such as X-rays, gamma rays, or accelerated particles, hard, homogeneous, usually opaque compositions are produced having properties differing substantially from those of the polymers that are normally produced by polymerization of the monomers involved.

The invention in one aspect therefore resides in preparing novel compositions by a process which comprises, hot dissolution of one or more polymerizable vinyl-base monomer in one or more saturated hydrocarbon such as parafin, slowly cooling the resulting solution to form a stable homogeneous gel, and exposing the gel to ionizing radiations.

Efiective completion of the grafting process is indicated by the fact that no more parafiin is migrating out of the composition.

The invention will now be described with reference to the following examples which are illustrative only, but not restrictive. In the examples, the parafiin stock used as the carrier constituent, is a mixture melting in the range 60-62 C., and the monomers used are vinyl acetate (Examples 1 and 2 show ditferent proportions of this monomer), styrene and methyl methacrylate.

EXAMPLE 1 An amount of cc. of vinyl acetate having 2 grams parafl'in incorporated therein is carried in a test tube to 50 C. The resulting solution is slowly cooled to 20 C. and a gel is obtained.

The tube containing the gel is sealed, but not evacuated, and is then exposed to gamma rays from a source of cobalt 60, until a dose of 1,500,000 roentgens has been applied. The resulting product is hard and translucent, and will hereinafter be termed composition A.

EXAMPLE 2 The procedure is the same as in Example 1, except that 10 g. paraffin are incorporated in 100 cc. vinyl acetate. The result is composition B.

EXAMPLE 3 Same procedure 'again, using 2 grams parafiinin 100 cc. styrene. Composition C is obtained.

EXAMPLE 4 The same procedure is used as above, but with 10 grams paraffin incorporated in 100 cc. methyl methacrylate. The resulting composition is termed composition D.

The physical and physico-chemical characteristics of compositions A, B, C and D are indicated in the following table.

By way of comparison, the same characteristics are also included for each of the following known compositions:

Vinyl acetate homopolymer, called composition E.

Styrene homopolymer (polystyrol), called composi tion F.

Methyl methacrylate homopolymer, called composition G."

Patented May 16, 1961 Table Characteristics Composition Composition Composition Composition Composition Composition Composition A B O D E F G Softening point, C 147 5? 09 147 25 Q) 135. Melting point, C sogtie lgsit 260 16st,; angirgguid 1m 1 soft at 300 0. Resistance to boiling water resists softens softens resists complete desoftens softens slightly. formation. slightly. Resistance at ordinary temperature Alcohol" swell resists do dissolves resists resists.

Ketones dissolves gel aswells disffl vas do dissolves dissolves.

Fsters do sw softens di s lvesilu do sw swells.

Perchlorethylene resists do dissolves resis sw l dissolves resists.

White spirit swells resligis when re ists do resis r i Do.

Xylene dn swells dissolves ..do dissolves dissolv dissolves. RelsIigtafice to alkel'm (concentrated resis resis r i do resists resis Do. 7 Resistance to acids:

Concentrated H2804 diluted 4 do do do is attacked-.." --...do resists.

Cg entrated H 80 is attacked is attacked.... do is attacked do d is attacked. Water absorption (percent at 20 C., 0.2- 4 o 0.3 10 o 0.3.

24 hrs.).

Referring to the above table, it will be noted that the gel to high energy, ionizing radiations until it has rechief advantages of the grafted copolymer compositions ceived a total dose of 1,500,000 roentgens. obtained according to the invention over corresponding 25 2. The method of producing novel copolymer composihomopolymers of the monomers respectively used, can tions which comprises preparing an intimate mixture be listed as follows: at approximately 50 degrees C. of at leastone vinyl (1) In the case of styrene, temperature resistance is base polymeriz l monomer With a Pafafilllic hydroimproved as indicated by comparison of the Softening carbon composition of at least one hydrocarbon of the points of compositions C and F, type C H containing not more than 20 percent of (2) In th case of vinyl a etate, improved water reunsaturated hydrocarbons as impurities therein and havsistance is indicated by comparison between compositions g a boiling point above 300 C. and a melting point A and B on one hand, composition E on the other. below 70 C., cooling said mixture slowly to 20 C. so

(3) In the case of methyl methacrylate, resistance to as to Set into Stable homogeneous 8 and exposing alkalis and acids is substantially improved as shown by said gel to high energy, ionizing radiations until it has comparison of compositions D and G. received a total dose of 1,500,000 roentgens.

The novel compositions can be worked by conventional 3- AS a novel composition of matter, a copolyme methods and machines, including molding, injection, com- Pr d ording to the method of claim 2. pression and extrusion. When dissolved they can be The method Claimed in claim wherein Said Vinyl spun or coated upon any suitable surface. 40 base monomer is liquid at ordinary temperature.

It will be apparent that the invention is not limited 5- The method claimed in claim 2, wherein said vinyl to the specific compositions, ingredients and proportions as 1110 is Selected from the g p consisting of specified herein, and that those skilled in the art on be- Vinyl acetate, Styrene and methyl methacl'ylatecoming acquainted with the teachings of the presentinvention will be able to conceive various modifications References Cited in the file of this P t therein within the scope of the ensuing claims. FOREIGN PATENTS What I claim is:

l. The method of producing novel polymer composi- 750923 Great Bntam June 20"1956 tions which comprises preparing an intimate mixture at DTHER REFERENCES approximately degrees C. of at least one vinyl base 50 polymerizable monomer with a paraflinic hydrocarbon Ballantine et al.: Brookhaven National Laboratory Re composition of at least one hydrocarbon of the type Port October 1956' cnHznJrz, mntainjng not more than 20% of unsaturated Charlesby I: Proc. Roy. Soc. (London),- vol. 222A, hydrocarbons as impurities therein and having a boiling 6044; February 1954' point above 300 C. and the melting point below 70 Banantme? Modem Flashes, PP- 171-174.,

C., allowing said mixture to cool slowly to 20 C. so as to set into a stable homogeneous gel, and exposing said September 1957. a

Charlesby II: Nucleonics, pp. 18-25, June 1954. 

1. THE METHOD OF PRODUCING NOVEL POLYMER COMPOSITIONS WHICH COMPRISES PREPARING AN INTIMATE MIXTURE AT APPROXIMATELY 50 DEGREES C. OF AT LEAST ONE VINYL BASE POLYMERIZABLE MONOMER WITH A PARAFFINIC HYDROCARBON COMPOSITION OF AT LEAST ONE HYDROCARBON OF THE TYPE CNH2N+2, CONTAINING NOT MORE THAN 20% OF UNSATURATED HYDROCARBONS AS IMPURITIES THEREIN AND HAVING A BOILING POINT ABOVE 300*C. AND THE METLING POINT BELOW 70* C., ALLOWING SAID MIXTURE TO COOL SLOWLY TO 20*C. SO AS TO SET INTO A STABLE HOMOGENEOUS GEL, AND EXPOSING SAID GEL TO HIGH ENERGY, IONIZING RADIATIONS UNTIL IT HAS RECEIVED A TOTAL DOSE OF 1,500,000 ROENTGENS. 